1. Field of the Invention
The invention relates to a device having a hydraulic drive for civil engineering work, particularly a pile-driving or drilling. The invention also relates to a method for operation of a device having a hydraulic drive for civil engineering work, particularly of a pile-driving or drilling device.
2. The Prior Art
In construction, different devices having a hydraulic drive for civil engineering work are operated in a hydraulic group. The hydraulic group generally consists of a hydraulic pump, preferably having a changeable displacement (adjustable pump), which is driven by a drive motor, for example an internal combustion engine, a work device having a hydraulic drive, for example a hydraulic motor, as well as a control or regulation unit. The hydraulic group is operated with a fluid in a hydraulic circuit. The product of pressure and volume stream of the fluid yields the hydraulic power.
Vibration pile-drivers, for example are used as work devices to introduce objects, such as, for example, profiles, into the ground or to pull them out of the ground, or also to compact ground material. The ground is excited by means of vibrations and thereby achieves a “pseudo-liquid” state. By means of a static top load, the goods to be pile-driven can then be pressed into the construction ground. Vibration pile-drivers generally have vibration exciters that act in linear manner, whose centripetal force is generated by means of rotating imbalances. The progression of the speed of the linear vibration exciter corresponds to a periodically recurring function, for example a sine function.
The vibration exciters are operated with hydraulic rotary drives, which put the shafts on which the imbalances are disposed into rotation. The required drive power can differ significantly during operation. For example, different ground composition properties or different goods to be pile-driven require different drive powers. In idle, on the other hand, the required drive power is very low. There are frequent situations in which the maximal power offered by the hydraulic circuit is not required or cannot be implemented. In the case of conventional vibration exciters having hydraulic motors, which do not have a changeable displacement (constant motors), the work pressure drops at a constant volume stream, while the power losses in the hydraulic circuit, which are dependent on the volume stream, remain constant.
In the case of vibration exciters having hydraulic motors with a changeable displacement (adjustable motors), operation in different speed of rotation ranges, without a power drop, is possible, as is known to a person skilled in the art from European Patent Application No. EP 2085149 A1.
Other devices used in construction, having a hydraulic drive, are so-called drilling devices. These are used, among other things, for the production of pile foundations, for example drilled piles and concrete piles for increasing the bearing capacity of the construction ground or for ground replacement measures. The drilling drives connected with the drilling device are generally hydraulic rotational drives, to which a drill pipe or drilling tools is/are attached.